1. Field of the Invention
The present invention relates to a liquid ejection head, a liquid ejection head cartridge incorporating the liquid ejection head, a printing apparatus employing the liquid ejection head cartridge, a printing system employing the printing apparatus, and a fabrication process of the liquid ejection head.
2. Description of the Related Art
A printing apparatus, such as an ink-jet printer, has a liquid ejection head, i.e. an ink-jet head including an ejection energy generating means for heating a liquid in a liquid passage and whereby ejecting the liquid from an ejection opening. The ink-jet head is a major portion constructed with a head chip having a liquid chamber, to which the liquid is supplied, and an electric wiring substrate, to which the head chip is connected. In the head chip, an electrical wiring for applying an electrical pulse to an electrothermal transducer as the ejection energy generating means for heating the liquid in each liquid passage, is built-in. In order to minimize the electrical wiring on the ink-jet head side, there has been known the head chip, in which an IC is built-in, or in which wiring corresponded to the electrothermal transducer are provided in one-by-one basis and an IC is mounted on the electrical wiring substrate side.
When the head chip of the ink-jet head and the electrical wiring substrate are assembled, it has been typically employed, in the prior art, to connect the head chip to a print circuit board as the electric wiring substrate by wire bonding, or to fit a predetermined mating surface of the head chip onto a flexible print circuit board as the electric wiring substrate under pressure.
However, in mass production of the ink-jet head, these method form the individual ink-jet heads in the connected condition, to require substantial work load, such as transportation or the like, in the subsequent process, and requires a large number of sets of various devices to require substantial investment for facilities. When the individual ink-jet head has relatively large number of wiring, it becomes necessary to provide large area for the connecting portion of lead terminals, namely to provide large dimension of the head chip in the width direction to cause high parts cost.
From the point of view, TAB (tape automated bonding) system, in which chip installation holes are intermittently formed through the electric wiring substrate integrated with a carrier film, and the head chips are placed on the chip installation holes to connect therebetween, has become widespread.
A configuration in plan view of the ink-jet head produced by the TAB system is illustrated in FIG. 15, and a section taken along line XVI--XVI is shown in FIG. 16, and a configuration in plan view of the condition where the head chip and the electric wiring substrate are connected but a seal resin is not yet applied, is illustrated in FIG. 17. At a center portion of an electrically insulative film form electric wiring substrate 11, a chip installation hole 13 having the same corresponding to an outer contour of a head chip 12 is formed. A plurality of lead terminals 14 having tip ends to be fitted on the head chip 12 are projected from the inner periphery of the chip installation hole 11. With these tip ends of the lead terminals 14, not shown connection electrodes exposed on the surface of the head chip 12 are mated with each other for establishing electrical connection therebetween. A seal resin 16 is applied over the chip head 12 and the electrical wiring substrate 11 so as to seal the connecting portion.
In the ink-jet head, ejection openings 15 for the liquid are arranged at the center portion of the head chip 12. Therefore, the seal resin 16 has to be applied without blocking these ejection openings 15.
When the ink-jet head shown in FIGS. 15 and 16 is produced by the TAB system, the seal resin 16 cannot be applied for the portion where the lead terminals 14 are not projected from the inner periphery of the chip installation hole 13. If attempt is made to apply the seal resin 16 between the head chip 12 and the chip installation hole 13 over the entire circumference of the head chip 12, the seal resin 16 should penetrate into the back side of the electric wiring substrate 11 through a gap portion S where the lead terminal 14 is not present to make it impossible to maintain the ink-jet head in normal configuration. Furthermore, since there is a portion where the seal resin 16 cannot be placed between the electric wiring substrate 11 and the head chip 12, sufficiently high strength in connection cannot be provided.
Thus, since the gap S where the seal resin 16 is not interposed between the head chip 12 and the chip installation hole 13, when another resin is injected around the head chip 12 after formation of seal by the seal resin 16 of the connecting portion between the connection electrodes and the lead terminal 14, the resin should form meniscus should be formed at the end of the gap portion S to prevent the resin from being injected smoothly. This causes a part of the liquid ejected from the ejection opening 15 to penetrate into the end portion of the gap portion S to cause corrosion on the TAB lead for forming electrical wiring of the head chip 12 to cause failure, such as breakage of the circuit and the like.
It may be considered to make the width of the gap portion S smaller. However, in view of the current status of technology of processing of the chip installation hole 13, processing with quite high precision in the extent to significantly restrict getting around of the seal resin 16.